Talking about the 4.0 here. Just put a new engine in my jeep and did a cluster swap at the same time so I have a tach now. Running 31s on the stock 5 spd with 3.55, and I notice that I hardly ever get it up to 3K rpm in everyday driving, and even when I get on it, never get close to redline. I guess I'll look for some dyno graphs and find out where the powerband end, because it sure feels like it's just spooling the engine and not gaining a whole lot of power in the upper rev range.
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How high do you rev your engine?
- Thread starter xj2win
- Start date
PurpleCherokee
NAXJA Forum User
- Location
- MO
Torque does tend to drop off pretty drastically in the upper-RPM range on a stock motor. Where you'll REALLY feel the torque is if you punch it from about 45-50 then slam the shifter into 1-2 and let the torque converter lock up. You're RPM's should be right around 3800 initially (which is where peak torque is at), then the torque converter should let it stay in the band for a little longer, putting your back in the seat a little longer. However, the power won't last long cause like I said, it drops off pretty quick. UNLESS... you do what I did w/my exhaust set up, then the power continues all the way to the redline :firedevil
mjma
NAXJA Forum User
- Location
- Rehoboth, MA
You're problem is the 3.55s and the 31s. They're alright, but not ideal. Ideally you want the 4.0L to be at about 2500 rpm cruising, for best gas mileage. I have an XJ on Q78s that gets better gas mileage that my XJ on 32s because the 32s are run with 3.55 gears and the Qs are with 4.88s.
My XJ on the 32s runs just over 2k on the highway. Even if I go up from 65 to 75, the rpms don't go up that much at all!!
The solution is to regear and put the RPMs back into the sweet spot.
In terms of redline, I don't believe I've ever gotten either jeep near redline. The highest is probably 4k, if it even made it that far. I wouldn't want to hold it past 4k for long at all.
My XJ on the 32s runs just over 2k on the highway. Even if I go up from 65 to 75, the rpms don't go up that much at all!!
The solution is to regear and put the RPMs back into the sweet spot.
In terms of redline, I don't believe I've ever gotten either jeep near redline. The highest is probably 4k, if it even made it that far. I wouldn't want to hold it past 4k for long at all.
XJ Stryker
WHO DAT!
- Location
- Smiths Station, Al
You also feel the torque when you are in first gear and you pushing over a rock and then CRUNCH crunch there goes your air dam.
:variety:
:variety:
PurpleCherokee
NAXJA Forum User
- Location
- MO
Haha, nice... jerk :laugh:
mjma said:
I know I aught to regear it, but I'm going to wait before sinking money into the stock axles, as I'm thinking about locking it and running 33s, but I'm a little nervous about 33s on the stock axles. I don't do a lot of hard wheeling, there are next to no rocks around here. 80% of the road the jeep sees is paved, and the offroading is usually through the woods.
XJ Stryker
WHO DAT!
- Location
- Smiths Station, Al
Sorry couldnt resist all in fun...:firedevil
mjma
NAXJA Forum User
- Location
- Rehoboth, MA
xj2win said:
What rear axle do you have?? The front is fine for 33s. If you have the 8.25, that is fine for 33s as well.
With 33s, you'll definitley want to regear. I recommend locking them as well. The rear, if it's an 8.25, will be fine, and the front should be fine as long as you don't romp on it with the wheel cranked. If so, then just make sure you've got spare front axle shafts. I run Q78s on the Dana 30 with 4.88s and have been lucky enough to just pop Ujoints here and there and change them out right away without any damage to anything else. Just know your jeep isnt' totally indestructable, wheel accordingly, and you'll be fine.
Running Dana 35 in the rear :thumbdown:
I was only planning on locking the rear, I don't run much extreme stuff, like I was saying, mostly in the woods, the toughest thing I've got to deal with is logs, stumps, and deep snow. Hopefully one locker should suffice for what I do, I'd rather leave the front open so I can utlize the tight turning radius.
I was only planning on locking the rear, I don't run much extreme stuff, like I was saying, mostly in the woods, the toughest thing I've got to deal with is logs, stumps, and deep snow. Hopefully one locker should suffice for what I do, I'd rather leave the front open so I can utlize the tight turning radius.
megabyte5689
NAXJA Forum User
- Location
- Kansas
I floor it from a stop light and get it to the max point until it shifts. I get told by friends that I shouldn't do this on a 200,000 mile motor
mjma
NAXJA Forum User
- Location
- Rehoboth, MA
33s, a locker, and a Dana 35 don't get along so well. You could run 33s open on a dana 35 if you were careful. Best bet is to grab an 8.25 or an 8.8 and throw that in there. You can lock either one of those axles and be fine on 33s. I've got an 8.25 in my driveway that I picked up for 50 bux, just incase I ever do sell one of my XJs I don't have to sell it with the Dana 44 in there!
